From c5b095ecf832f411f60e503262505255db0230ce Mon Sep 17 00:00:00 2001 From: Daniel Stenberg Date: Fri, 23 Sep 2016 14:44:11 +0200 Subject: [PATCH] deps: avoid single-byte buffer overwrite MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Incorrect string length calculation when passing escaped dot. - CVE: CVE-2016-5180 - Upstream bug: https://c-ares.haxx.se/adv_20160929.html Ref: https://github.com/nodejs/node/pull/9037 PR-URL: https://github.com/nodejs/node/pull/8849 Reviewed-By: Myles Borins Reviewed-By: James M Snell Reviewed-By: Johan Bergström Reviewed-By: Fedor Indutny --- deps/cares/src/ares_create_query.c | 84 ++++++++++++++---------------- 1 file changed, 39 insertions(+), 45 deletions(-) diff --git a/deps/cares/src/ares_create_query.c b/deps/cares/src/ares_create_query.c index 8624e2f589bbb3..abae64a0462c82 100644 --- a/deps/cares/src/ares_create_query.c +++ b/deps/cares/src/ares_create_query.c @@ -85,57 +85,31 @@ */ int ares_create_query(const char *name, int dnsclass, int type, - unsigned short id, int rd, unsigned char **buf, - int *buflen, int max_udp_size) + unsigned short id, int rd, unsigned char **bufp, + int *buflenp, int max_udp_size) { - int len; + size_t len; unsigned char *q; const char *p; + size_t buflen; + unsigned char *buf; /* Set our results early, in case we bail out early with an error. */ - *buflen = 0; - *buf = NULL; + *buflenp = 0; + *bufp = NULL; - /* Compute the length of the encoded name so we can check buflen. - * Start counting at 1 for the zero-length label at the end. */ - len = 1; - for (p = name; *p; p++) - { - if (*p == '\\' && *(p + 1) != 0) - p++; - len++; - } - /* If there are n periods in the name, there are n + 1 labels, and - * thus n + 1 length fields, unless the name is empty or ends with a - * period. So add 1 unless name is empty or ends with a period. + /* Allocate a memory area for the maximum size this packet might need. +2 + * is for the length byte and zero termination if no dots or ecscaping is + * used. */ - if (*name && *(p - 1) != '.') - len++; - - /* Immediately reject names that are longer than the maximum of 255 - * bytes that's specified in RFC 1035 ("To simplify implementations, - * the total length of a domain name (i.e., label octets and label - * length octets) is restricted to 255 octets or less."). We aren't - * doing this just to be a stickler about RFCs. For names that are - * too long, 'dnscache' closes its TCP connection to us immediately - * (when using TCP) and ignores the request when using UDP, and - * BIND's named returns ServFail (TCP or UDP). Sending a request - * that we know will cause 'dnscache' to close the TCP connection is - * painful, since that makes any other outstanding requests on that - * connection fail. And sending a UDP request that we know - * 'dnscache' will ignore is bad because resources will be tied up - * until we time-out the request. - */ - if (len > MAXCDNAME) - return ARES_EBADNAME; - - *buflen = len + HFIXEDSZ + QFIXEDSZ + (max_udp_size ? EDNSFIXEDSZ : 0); - *buf = malloc(*buflen); - if (!*buf) - return ARES_ENOMEM; + len = strlen(name) + 2 + HFIXEDSZ + QFIXEDSZ + + (max_udp_size ? EDNSFIXEDSZ : 0); + buf = malloc(len); + if (!buf) + return ARES_ENOMEM; /* Set up the header. */ - q = *buf; + q = buf; memset(q, 0, HFIXEDSZ); DNS_HEADER_SET_QID(q, id); DNS_HEADER_SET_OPCODE(q, QUERY); @@ -159,8 +133,10 @@ int ares_create_query(const char *name, int dnsclass, int type, q += HFIXEDSZ; while (*name) { - if (*name == '.') + if (*name == '.') { + free (buf); return ARES_EBADNAME; + } /* Count the number of bytes in this label. */ len = 0; @@ -170,8 +146,10 @@ int ares_create_query(const char *name, int dnsclass, int type, p++; len++; } - if (len > MAXLABEL) + if (len > MAXLABEL) { + free (buf); return ARES_EBADNAME; + } /* Encode the length and copy the data. */ *q++ = (unsigned char)len; @@ -195,14 +173,30 @@ int ares_create_query(const char *name, int dnsclass, int type, DNS_QUESTION_SET_TYPE(q, type); DNS_QUESTION_SET_CLASS(q, dnsclass); + q += QFIXEDSZ; if (max_udp_size) { - q += QFIXEDSZ; memset(q, 0, EDNSFIXEDSZ); q++; DNS_RR_SET_TYPE(q, T_OPT); DNS_RR_SET_CLASS(q, max_udp_size); + q += (EDNSFIXEDSZ-1); + } + buflen = (q - buf); + + /* Reject names that are longer than the maximum of 255 bytes that's + * specified in RFC 1035 ("To simplify implementations, the total length of + * a domain name (i.e., label octets and label length octets) is restricted + * to 255 octets or less."). */ + if (buflen > (MAXCDNAME + HFIXEDSZ + QFIXEDSZ + + (max_udp_size ? EDNSFIXEDSZ : 0))) { + free (buf); + return ARES_EBADNAME; } + /* we know this fits in an int at this point */ + *buflenp = (int) buflen; + *bufp = buf; + return ARES_SUCCESS; }